The invention relates to track fittings for use in anchoring loads to the floor of aircraft. Typically, an aircraft floor includes a plurality of parallel, longitudinally slotted, channel-like tracks arranged flush with the floor down the length of the interior. The tracks have alternate wide and narrow openings which are commonly spaced at a one inch pitch so that fittings for anchoring seats or cargo can be located at any desired multiple inch increment along the length of the track. The fittings and associated track must typically be able to support 4,000 pound vertical and 3,600 pound horizontal loads. One commercially available fitting which meets these requirements comprises a housing which carries a vertically movable shear pin and an operating handle therefor at its forward end and a pair of threaded, headed retaining studs on one inch centers at its rearward end. The headed studs are adapted to be slid under retaining lips in the track and the shear pin is then lowered into the wider openings in the track to prevent forward movement. A transverse aperture is located in the housing midway between the studs for attaching a load to the fitting. The lockable fittings being discussed are usually, when used on a seat, only used on the rear legs of the seat. The front legs are usually attached to the rear legs by a metal strap member and to the seat track by non-lockable fittings. In order to facilitate mounting of the fittings to the floor track, it is customary to provide a small amount of clearance between the interengaging portions of the fitting and the floor track. Unfortunately, the clearance often permits the seat to rattle in the track or be moved slightly by fore or aft forces applied to it by its occupants. The rattling of the fitting can be quite annoying to passengers and the continual movements can result in accelerated wearing of the track and studs.
Various fittings have been proposed to eliminate rattling. Weik U.S. Pat. No. 4,062,298 discloses a relatively lengthy fitting in which the shear pin is moved up and down in a vertical slot in the housing by a pin which is mounted in two pairs of slots and positively advanced by turning a horizontal screw. In the fitting's tightened position, a pad carried by the shear pin presses down on the top of the track as the fitting body is lifted to force the tops of the studs against the bottom of the track lips. Howell U.S. Pat. No. 4,230,432 discloses a shorter fitting where the shear pin is positioned between two fixed studs and is threadedly moved down to engage a track slot and to cause a pad on the shear pin to press down on the top of the track as the fitting body is lifted to force the studs against the bottom of the track lips. Grendahl U.S. Pat. No. 4,109,891 shows a high strength fitting which has four studs on two pivoted plates and an adjustment screw to pivot one plate relative to the other for preventing rattling.